Conventionally, as a power supply wiring structure for supplying power to a semiconductor integrated circuit (hereafter “LSI”), for example, a technology disclosed in JP-A-2006-173418 is known. According to this technology, a power supply wiring structure includes a first wiring layer in which a plurality of power supply voltage supply wires (hereafter “power supply voltage wires”) and a plurality of reference voltage supply wires (hereafter “ground wires”) are alternately disposed; a second wiring layer in which a plurality of power supply voltage wires and a plurality of ground wires are alternately disposed in a direction perpendicular to the wiring direction of the first wiring layer; and an insulating layer disposed between the first wiring layer and the second wiring layer (hereafter “meshed power supply wiring structure”). In the meshed power supply wiring structure, parasitic capacitance is formed at the overlapping portions (intersecting portions) of the power supply voltage wires of the first wiring layer and the ground wires of the second wiring layer, or at the overlapping portions of the ground wires of the first wiring layer and the power supply voltage wires of the second wiring layer, via the insulating layer. The parasitic capacitance can be utilized as a capacitance for decreasing power supply noise.
However, as a result of increases in LSI clock frequency that have been achieved in recent years, the parasitic capacitance of the conventional meshed power supply wiring structure cannot be necessarily expected to provide the power supply noise reduction effect with respect to a desired frequency bandwidth. In addition, with the latest LSI design rules demanding ever finer features, when the LSI power supply wiring has the mesh structure, the transmission paths of a signal line system in the LSI have high characteristic impedance. As a result, in the case of a relatively long wiring, a mismatch may occur between the output impedance of the transistors in the LSI and the characteristic impedance of the transmission path, resulting in noise. Furthermore, the relatively long transmission path with such high characteristic impedance may act as an antenna that picks up noise. Meanwhile, with regard to the power supply impedance at a high frequency of the LSI power supply (the impedance on the power supply side as viewed from LSI), because of the mesh structure, the wiring resistance (series resistance) of the power supply may become too high to ignore. This has resulted in cases where the expected operation of the LSI at high frequency cannot be obtained due to the parasitic inductance and parasitic wiring resistance in the power supply wiring network.